Radio Frequency Identification (RFID) devices are low-cost, “smart” chips or “tags” that can be embedded in or attached to articles, products, and the like, to convey information about the product via a scanner. The RFID tags are generally small label-like devices with a microchip or data circuit and a miniature embedded antenna. The tags may be passive or active, the active tags requiring an internal power supply. A reader or scanner interrogates the RFID tag with an electronic “trigger” signal. The tag in turn generates an electromagnetic pulse response that is readable by the scanner, the response containing any manner of product information. From a manufacturing or material handling standpoint, RFID tags can be embedded directly in raw material packaging, on pallets or shelves, at various warehouse locations, and so forth, to convey any manner of information related to materials, storage locations, production schedules and uses, and the like.
Implementation of RFID systems with material handling equipment such as forklifts, clamp trucks, lift trucks or hoists, and the like, offers advantages in various aspects of manufacturing, from inventory control to improved production efficiencies. Various patent publications describe the use of RFID systems with such equipment, including: U.S. Pat. Nos. 7,155,304; 7,121,457; 7,151,979; 6,669,089; US Pat. Appln. Pub. 2006/0255948; US Pat. Appln. Pub. 2006/0255954; US Pat. Appln. Pub. 2006/0255951; US Pat. Appln. Pub. 2005/0200457; and US Pat. Appln. Pub. 2006/0287759. These cited patents and applications pertain to various configurations of RFID devices on conventional lifting devices to address particular perceived shortcomings, or to improve material handling.
Many facilities typically handle relatively tall stacks of light materials or products with conventional lifting devices in the course of product manufacture, packaging, transport, and so on. These materials or products may be, for example, cartons of bulky consumer goods or large rolls of pre-formed absorbent raw material (referred to collectively as “articles”). The height of such articles, stacked or individually packaged, may significantly exceed the effective height of the clamp region between the clamps of a conventional clamp truck, or the back support of the carriage assembly of a conventional forklift. In this situation, use of RFID antennas on or around the clamps and back support of the lifting device may result in miss-reads of articles at the top of the stack due to the relatively limited range of the RFID tag antennas, or interference from the products or pallets on the stack or surrounding the stack. Increasing the signal strength of the RFID antennas for tags associated with all of the articles so as to increase the effective interrogation range of the articles should the articles end up at or near the top of a stack is not a viable solution. Spurious detection of articles in nearby stacks or storage locations will likely occur, resulting in serious degradation of the handling system integrity and efficiency.
Simply placing RFID scanner antennas on the mast of the lifting device, or on other elevated structure, is also not acceptable. There is relatively limited space between the stationary and vertically moving components of conventional clamp trucks or forklifts to effectively accommodate the antennas. Also, additional support structure attached to the mast for attaching the scanner antenna may result in impairment of the operator's visibility. In addition, the mast does not move in the same manner as the clamps or carriage assembly and, after elevating the clamp or carriage, the mast antenna may actually be disposed below the clamps or carriage and thus be ineffective in reading RFID tags on articles in the elevated stack.
The lifting device RFID configurations discussed in the publications cited above fail to address the issues of moving or handling relatively tall stacks of articles with conventional lifting devices, and a need exists in the industry for a solution to these concerns. The present invention relates to such a solution.